The present invention relates to a map image processing technique which handles road map data, and more particularly to a device and method for preparing road map data.
Electronic map techniques in which a computer is used to display electronic map image data on a screen are utilized in various applications including car navigation. In cases were roads are displayed on ordinary maps, there is no problem if the roads are drawn as simple lines ignoring the width of the roads in the case of small-scale maps such as large-area maps. However, in the case of large-scale maps such as detailed city maps, roads must be expressed as regions that have an accurate width dimension. Naturally, in the case of electronic maps as well, various road data preparation methods and display methods have been developed for the purpose of expressing roads with a width dimension. For example, the methods described in Japanese Patent Application Kokai No. Sho 62-80774, Japanese Patent Application Kokai No. Hei 4-303271, Japanese Patent Application Kokai No. Hei 4-303272 and Japanese Patent Application Kokai No. Hei 6-83931, etc., are known.
In the graphic processing device described in Japanese Patent Application Kokai No. Sho 62-80774, the trouble involved in drawing roads by the manual setting one at a time of straight lines that constitute road outlines in the preparation of road maps that show a width dimension in the roads is eliminated as follows: specifically, when the drawer sets the road width at the starting point and final point of a road, a pair of parallel lines that run from the starting point to the final point while maintaining a spacing that corresponds to the road width are drawn, and in cases where a given pair of parallel lines crosses another pair of parallel line, the parallel lines at the point of intersection are automatically erased. Accordingly, road maps with a width dimension that encompasses intersections can easily be prepared.
In the device described in Japanese Patent Application Kokai No. Hei 4-303271, when a person sets the road width and draws a reference line with a cursor, a pair of parallel lines are drawn that run along this reference line while maintaining a spacing that corresponds to the road width.
In the device described in Japanese Patent Application Kokai No. Hei 4-303272, when two road s that are respectively expressed as pairs of parallel straight lines partially overlap each other at an angle, the parallel lines are amended in the overlapping area s o that a turning angle is drawn.
In the device described in Japanese Patent Application Kokai No. Hei 6-83931, when two roads that are respectively expressed by pairs of parallel lines are connected with each other, the connecting parts between the roads are drawn using pairs of parallel straight lines and arc-form lines.
Thus, in the prior art, road data is expressed by pairs of parallel lines. However, actual road shapes are extremely complex, and the accurate expression of such shapes by means of pairs of parallel lines alone is absolutely impossible. Especially in the case of extremely large-scale city maps in which center dividers, sidewalks and traffic lanes, etc., are accurately drawn, conventional road data preparation techniques using pairs of parallel lines are completely useless.
Furthermore, in the case of electronic city maps, there is a demand for a system that allows the automatic painting in of roads with colors or textures. In the case of paper-based city maps, roads may be made easily visible by coloring the roads with colors that are different from those of other regions. In electronic maps as well, roads are naturally easier to see if these roads are colored with specified colors. In order to achieve automatic painting in of roads, the roads must be expressed by open-loop polygonal data However, conventional road data is merely a collection of simple line segments such as parallel lines and arc-form lines, etc. As a result, the painting in of roads cannot be performed automatically. Accordingly, in conventional electronic city maps, buildings, etc., expressed by polygons are painted in with specified colors, while roads are merely indicated by drawing the outlines of the roads, with no special coloring being applied.
Furthermore, electronic maps can provide convenient functions such as alterations in scale and street search, etc. For example, in car navigation systems, a method of use is possible in which a street search is performed and a route is displayed on a map, with the vehicle being caused to run along this route; during this operation, a small-scale large-area map is displayed while the vehicle is running on high-speed roadways, and when the vehicle enters an urban area, the display is switched to a large-scale city map. In this case, if the route found as a result of the search runs along (for example) road A, then the route must be displayed on the same road A in both the large-area map and city map. Accordingly, it is necessary that there be a logical connection between the respective roads on the large-area map and the same roads on the city map. Generally, in the case of large-area maps, it is sufficient if roads are expressed as simple lines; accordingly, the road data in such a case is road network data in which points of intersection are expressed as nodes, and roads are expressed as vector data connecting these nodes. In the case of city maps, on the other hand, the road data is a collection of road outline line-segment data such as pairs of parallel lines and arc-form lines, etc., indicating the outlines of roads (as was described above). Conventionally, an association has been established between roads shown on city maps and roads shown on large-area maps by causing the center coordinates of intersections on city maps to correspond to the nodes of the road network data on large-area maps. As a result, however, even on city maps, routes found as a result of searching are simply expressed as zigzag lines connecting the center points of intersections; in such a case, it cannot be said that the advantages of city maps, which show road configurations in detail, are sufficiently obtained.
Accordingly, an object of the present invention is to accomplish the automatic preparation of road data which shows accurate agreement with complex road configurations.
A further object of the present invention is to accomplish the automatic preparation of road data using polygonal-shape data which paints in roads that have a width dimension.
Still a further object of the present invention is to accomplish the automatic preparation of road data which is associated with road network data used in large-area maps, and which accurately expresses the road configurations used in city maps.
Still a further object of the present invention is to solve several concrete technical problems described below, which arise in the development of practical techniques for achieving the abovementioned objects.
In the road data preparation device of the present invention, (1) simple road polygons which encompass roads that have a width dimension in city map data are produced from road network data in which intersections are expressed as nodes and roads are expressed as links that connect these nodes, (2) scissors data which defines the outlines of roads is prepared from city map data, and (3) road polygon data which is shaped into the shapes of roads in the city map data is prepared by trimming the simple road polygons along the outlines defined by the scissors data. As a result, the roads having complicated shapes in the city map are expressed as polygons.
In a preferred embodiment of the present invention, when a plurality of independent simple road polygons are prepared for a single link in the preparation of simple road polygons, these simple polygons are distinguished as external polygons that correspond to the external shapes of roads, and cut-out polygons that correspond to cut-out areas of roads. In this way, roads with loop shapes that have cut-out areas can also be favorably converted into polygons.
In a preferred embodiment of the present invention, simple road polygons that encompass roads on city maps are prepared by expanding the nodes and links of road network data to an extent that exceeds the width dimensions of roads on such city maps. In this case, the nodes are expanded to a greater extent than the links. Furthermore, the flexure points of links are also expanded to a slightly excessive degree. In this way, simple road polygons that also securely encompass locations that have a somewhat increased area, such as intersections and turning angles of roads, etc., can be prepared. After such simple road polygons that completely encompass the roads have been prepared, road polygons that show a good correspondence with the outline shapes of the roads can be obtained by trimming these simple road polygons with the scissors data that indicates the outlines of the roads, so that excess portions are removed.
In a preferred embodiment of the present invention, when scissors data is to be prepared, shape lines in the vicinity of roads in city map data are selected, those shape lines among the selected shape lines whose end points coincide with each other or are located in close proximity to each other are connected to each other, and the line-segment data obtained by this connection is used as scissors data In this way, scissors data that indicates road outlines in a favorable manner can be obtained.
In a preferred embodiment of the present invention, the device of the present invention further comprises a traffic lane preparation part which prepares a plurality of traffic lane polygon data expressing a plurality of traffic lanes from the abovementioned shaped road polygon data, and a guide line setting part which sets a guide line inside each of the abovementioned traffic lane polygon data.
In a preferred embodiment of the present invention, when it becomes necessary to display a road map of an area that forms a part of the overall map region covered by the aforementioned road network data, the aforementioned shaped road polygon data is dynamically prepared for roads contained only in the aforementioned partial area
The road map display device of the present invention comprises polygon road map data which includes road polygon data that expresses the roads that are to be displayed by means of respective polygons, and a display part which displays the aforementioned roads using the abovementioned road polygon data.
In a preferred embodiment of this road map display device, the polygon road map data further includes traffic lane polygon data which expresses respective traffic lanes within roads as polygons, and guide line data which expresses a guide line which is set within the respective traffic lanes, and the abovementioned display part not only displays roads, but also displays respective traffic lanes within the roads using the abovementioned traffic lane polygon data, and further displays a guide mark positioned within a selected traffic lane using the abovementioned guide line data.
A preferred embodiment of this road map display device further comprises road network data, city map data, and a road polygon data preparation part which dynamically prepares road polygon data on the basis of the road network data and the city map data for roads included in an area that is to be displayed in cases where it becomes necessary to display a road map of the area which forms a part of the overall map region covered by the abovementioned road network data.
The intersection polygon preparation device of the present invention receives road network data which has nodes that express intersections, and links between nodes that express roads between intersections, and city map data which has line-segment data that expresses the shapes of map elements as sets of shape element points. Furthermore, this device determines, in city map data, a specified search region that include nodes of interest in road network data, and searches within the determined search region for shape element points which are positioned so that these shape element points satisfy specified positional conditions. Next, using the shape element points that have been found as a result of the abovementioned search, this device prepares intersection polygon data for the abovementioned nodes of interest. Using this device makes it possible to prepare intersection polygon data automatically from road network data and city map data based on line segments. The intersection polygon data thus prepared inevitably has a data association with nodes in the road network data.
In a preferred embodiment, this device determines the abovementioned search region, and then splits this search region in to a plurality of sub-search regions using links connected to nodes, and determines inherent positional conditions as positional conditions for the respective sub-search regions. Then, this device searches in the respective sub-search regions for shape element points that satisfy the inherent positional conditions, collects the shape element points that are found in the plurality of sub-search regions, and prepares intersection polygon data. The respective sub-search regions include shape element points of the respective comer parts of intersections. Since the positional relationship between nodes of interest and the respective comer parts differs for each comer part, the shape element points of the respective comer parts can be securely extracted by determining inherent positional conditions that are suited to the respective comer parts for each sub-search region. Accordingly, accurate intersection polygon data can be obtained.
In a preferred embodiment, this device determines the proximate point that is closest to the node of interest in each of the plurality of sub-search regions within the aforementioned search region, and sets a band region which is separated from the node of interest by the distance range between a first distance extending from the node of interest to the proximal point and a second distance obtained by adding a specified permissible width to the first distance. Then, in each sub-search region, this device picks up only the shape element points present inside the band region as points that construct an intersection polygon. Accurate intersection polygons can be obtained with high precision by this method.
In a preferred embodiment, this device divides a city map region covered by city map data into numerous small cells, selects at least one cell that is located in close proximity to a position corresponding to the node of interest (e.g., the cell where the node of interest is positioned, or a cell adjacent to this cell) from the abovementioned cells as an object cell, and sets the abovementioned search region inside this object cell. The amount of data handled in the processing used to prepare respective intersection polygons is reduced by this method, so that the burden on the calculator used is lightened.
In a preferred embodiment, this device receives road map data that has road polygon data, and in cases where there are regions in which the road polygon data and the abovementioned intersection polygon data overlap, the aforementioned overlapping regions are removed from the road polygon data using the abovementioned intersection polygon data, so that pure road polygon data that does not overlap with intersection polygon data is prepared.
In a preferred embodiment, this device further determines a plurality of tangential lines that contact a plurality of roads from intersection polygon data, and extract two tangential lines from the plurality of determined tangential lines. Furthermore, within the polygon regions covered by the intersection polygon data, this device prepares substantially sector-shaped or substantially rectangular guiding intersection polygons that smoothly connect the two extracted tangential lines to each other.
Another road map display device of the present invention receives road map data that has road polygon data and guiding intersection polygon data, and selects road polygon data for a plurality of roads that are to be displayed and guiding intersection polygon data used to connect the abovementioned plurality of roads; then, the road map display device displays the abovementioned roads and intersections using the selected road polygon data and guiding intersection polygon data.
Another road map display device of the present invention receives road map data that has road polygon data and intersection polygon data, and also receives traffic jam information that indicates the end point position of a tailback of cars. Furthermore, this device selects road polygon data or intersection polygon data for a road or intersection in which the end point position of tailback of cars are present from the abovementioned road map data, and divides the selected road polygon data or intersection polygon data into a portion corresponding to an upstream side region and a portion corresponding to a downstream side region at the aforementioned end point position. Then, using the downstream side region of the split road polygon data or intersection polygon data, and road polygon data and intersection polygon data for roads and intersections which are located further downstream than the abovementioned downstream side region along the tailback of cars, this device displays the regions of roads and intersections in which the tailback of cars is present. As a result, the regions of roads on which there is a traffic jam can be accurately displayed.
The computer-readable data recording medium of the present invention accommodates polygonal road network data including node data and link data that are mutually associated so that a road network can be constructed. The respective node data include intersection polygon data in which the shapes of the intersections of the respective nodes are expressed by polygons; and the link data include road polygon data in which the shapes of the roads of the respective links are expressed by polygons.
By using the abovementioned polygonal road network data, the computer map application can prepare and display polygonal road map images in which the shapes and positions of roads and intersections drawn on city maps show good agreement. In addition, in cases where the map application performs processing such as route search and map matching, etc., using the abovementioned polygonal road network data, the basic portions of conventional route search or map matching algorithms using convention road network data can be utilized.
Another road map image display device of the present invention comprises the abovementioned polygonal road network data and a display part which receives this polygonal road network data and prepares and displays polygonal road images consisting of polygons that express intersections and polygons that express roads.
In a preferred embodiment, this road map display device further comprises city map data, and the abovementioned display part prepares city map images using this city map data, and displays the abovementioned polygonal road images superimposed on these city map images. Furthermore, the display part has the function of performing processing such as route search or map matching, etc., using the abovementioned polygonal road network data.
The present invention can typically be worked using a computer. Computer programs for this purpose can be installed or loaded into the computer using various media such as various types of disk storage, semiconductor memories or communications network signals, etc. The present invention can not only be worked using a single computer, but can also be worked by dispersed processing using a plurality of computers.